1. Field of the Invention
The laws of certain Provinces of Canada and of many European countries provide for taxes to be imposed on motive fuels, such as diesel oil, but a lesser tax or none at all on heating oil. In view of the fact that diesel oil and heating oil are very similar in their chemical and physical properties, it becomes necessary to mark, tag or otherwise identify the untaxed oils, or gasolines, from those that are taxed.
2. Description of the Prior Art
Furfural has been used widely as a marker for petroleum products for the purpose of tagging or identifying same. In fact, the laws of certain Provinces of Canada specifically require that furfural be used for this purpose.
The property of furfural to form colored compounds with primary aromatic amines in an acidic medium has been known for more than 100 years. One important application of the furfural color reaction is its use as a marker for petroleum fuels. A marker, or identifying agent is used to detect a fuel which may be subjected to differing tax rates, depending on its application, such as motor vehicle diesel engine fuel or light heating oil. Another application may be detection of blending lower priced or lower grade fuels into higher grade products. Examples are kerosene or low octane gasoline into higher octane gasoline.
The only well recognized reagent system for furfural detection in petroleum products is a solution of aniline in acetic acid (generally about 10% aniline). The reagent commonly is used by governmental agents in field test procedures by mixing about one volume part of reagent with 10 volume parts fuel sample in a clear container and shaking vigorously for a short time. Upon standing, the reagent layer settles to the bottom. For fuel samples containing furfural, the reagent layer is colored bluish red, with an intensity depending on furfural content. If no furfural is present, the reagent layer remains colorless.
With some elaborations, the field test procedure also can be modified to form the basis for quantitative laboratory furfural determination.
However, the preceding test description represents ideal conditions, frequently not encountered in reality. Furfural typically is employed at about 10 parts per million as a petroleum marker. Under very favorable circumstances, it is detectible at concentrations down to 0.5 parts per million, or approximately 5% marked fuel in a mixture with 95% unmarked fuel. Under common unfavorable conditions, the minimum test sensitivity may be only 2.0 parts per million, a situation preventing detection below 20% marked fuel. Since the area of 5%-20% marked fuel blending normally is of high interest to enforcement authorities improved test reagents are needed.
However, there are certain drawbacks with the conventional aniline/acetic acid reagent system, such as:
1. The aniline/acetic acid combination extracts appreciable impurities from fuel samples. These comprise both naturally colored materials and fuel components other than furfural that become colored on contact with the acidic reagent. They produce yellow to brown colors in the reagent, whose intensity obscures or masks a furfural color reaction, and in some situations may even produce a false positive test. PA0 The characteristics of light heating oils and gasolines in this respect vary widely so there is no way to predict the degree of interfering coloration resulting from any particular fuel sample. Additionally, the characteristics of a given fuel change wth age, particularly in products containing severely cracked fractions. PA0 2. A varying proportion of reagent is dissolved by the fuel sample. This ranges upward to almost 100% in some gasolines, effectively destroying the test by simply being difficult to see or by further concentrating fuel color impurities in the extract layer. PA0 3. Stability of the furfural reaction color varies widely, and is generally relatively shortest in the darkest, least stable fuels. Here, the true red furfural color commonly is altered to orange or orange-brown because of the superimposed natural color. The natural color increases rapidly on standing while the positive test shade becomes browner. As a result, weaker positive tests often are visible only for a few seconds, in unfavorable situations. PA0 4. Stability of the reagent itself. When aniline and acetic acid are mixed, the combination immediately begins to develop a yellow color. It increases more or less rapidly, particularly during the first 24-48 hours, and depending upon exposure to light, air and ambient temperature. As the color deepens to orange, loss of reagent efficiency takes place. PA0 Even though the reagent retains some activity for periods of a week to a month, the simultaneous development of interfering background color severely decreases test sensitivity. This problem limits use of prepacked test kits and reagent supplies that are desirable in practical applications. PA0 5. Aniline/acetic acid freezes at +16.degree. C., making it difficult or impossible to use in cold climates. The most important period wherein furnace oil is substituted in part or all for diesel fuel is during the winter months. Temperatures under field test conditions in areas where furfural is of interest, range to -30.degree. C., and are rarely above 0.degree. C. during the critical period. PA0 6. The aniline/acetic acid reagent is corrosive to the skin and possesses an offensive irritating odor. Both properties create resistance to use by law enforcement personnel. PA0 1. Extracts only a minimal amount of impurities from the petroleum product. PA0 2. Is essentially insoluble in petroleum products so that at least about 80 percent of the reagent volume used separates from the petroleum product with which it is mixed to form a separate recognizable layer. PA0 3. The duration and stability of the positive test color is increased under all test conditions. PA0 4. The test sensitivity is increased so that detection of furfural may be made at concentrations as low as about 0.25 part per million. PA0 5. The stability of the two-component liquid reagent is increased. PA0 6. The freezing point of each component of the two-component liquid reagent is below -40.degree. C., thus making possible cold weather testing. PA0 7. Each component of the two-component liquid reagent is less corrosive to the skin than the aniline/acetic acid reagent. PA0 First Component PA0 Second Component
Accordingly, it would be desirable and is an object of this invention to provide a reagent for the detection of furfural in petroleum products, which reagent overcomes the aforenoted disadvantages of an aniline/acetic acid reagent, and has the following advantageous characteristics:
The fulfillment of these desiderata and object of this invention may be more readily appreciated by reference to the following specification, examples and appended claims.